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Multi-dimensional interferometric amplification of ultrashort laser pulses

Periodic Reporting for period 3 - MIMAS (Multi-dimensional interferometric amplification of ultrashort laser pulses)

Reporting period: 2018-09-01 to 2020-02-29

Laser systems emitting ultrashort pulses have become an indispensable tool for a wide variety of applications in industry and science. However, the performance of state-of-the art systems is limited by a variety of physical effects, which makes the realization of the most demanding applications, e.g. high-repetition rate laser particle acceleration currently impossible. The approach in this project to overcome these issues is to use massively parallelized arrays of fiber-based amplifications channels. These amplification channels are embedded in a single fiber, making compact and stable systems possible. In order to generate a single laser beam from such an array, their output beams are coherently combined using integrated beam combiners and the pulses temporally overlapped correctly using a novel phase stabilization algorithm. In summary, parallelization of laser amplifiers offers the possibility to meet the challenges of todays and tomorrows applications.
We have successfully realized the first prototype of a laser amplifier based on the proposed technologies. An optical fiber has been designed and manufactured containing a 4x4 array of cores that guide and amplify the laser pulses. We have also designed and acquired a compact 1:16 beam splitter and combiner and a piezo driven array of 16 mirrors that can control the optical phase of each beam individually. With a novel algorithm, the phase of each beam is controlled that all beams recombine into a single output beam at the beam combiner.
In addition to the coherent combination of laser beams, the temporally separated amplification of multiple pulses, followed by a combination process, also provides a performance scaling opportunity for the pulse parameter. Traditionally, this pulse train is artificially created with a number of optical delay lines, mirroring the delay lines necessary for combination. We have developed a setup that can combine the pulses generated by the oscillator of the laser system, thereby making the laser systems more compact and robust. A first demonstration of this technology has been realized.
In accordance to the original proposal, a major focus will be to increase the number of amplification channels in a single fiber and develop the components required for coherent combination to support this higher channel count. Work has also started to use micro-structured cores in the fiber, which will make it possible to increase their diameter without sacrificing the beam quality. In combination with the developing temporal pulse combination system, we intend to achieve a J-class femtosecond laser with multi-kW average power.
International group of participants of the MIMAS workshop (rights: Fraunhofer IOF)
official MIMAS Logo
Construction of the 16-channel fiber laser system (rights: FSU Jena, Kasper)